Natural products are substances produced by microbes, plants, and other organisms. Microbial natural products offer an abundant source of chemical diversity, and there is a long history of utilizing natural products for pharmaceutical purposes. Despite the emphasis on natural products for human therapeutics, where more than 50% are derived from natural products, only 11% of pesticides are derived from natural sources. Nevertheless, natural product pesticides have a potential to play an important role in controlling pests in both conventional and organic farms. Secondary metabolites produced by microbes (bacteria, actinomycetes and fungi) provide novel chemical compounds which can be used either alone or in combination with known compounds to effectively control insect pests and to reduce the risk for resistance development. There are several well-known examples of microbial natural products that are successful as agricultural insecticides (Thompson et al., 2000; Arena et al., 1995; Krieg et al. 1983).
The development of a microbial pesticide starts with the isolation of a microbe in a pure culture. It then proceeds with efficacy and spectrum screening using in vitro, in vivo or pilot scale trials in a greenhouse and in the field. At the same time, active compounds produced by the microbe are isolated and identified. For the commercialization of a microbial pesticide, the microbe has to be economically produced by fermentation at an industrial scale, and formulated with a biocompatible carrier and approved additives to increase efficacy and to maximize the ease of application.
Uses of Bacillus megaterium, and Products Produced Therefrom.
Bacillus megaterium is a Gram-positive bacterium that grows in simple media and on more than 62 out of 95 carbon sources, such as tricarboxylic acid cycle intermediates (e.g., formate and acetate), and forms spores mainly under aerobic conditions (see, for example, Vary, 2007). It has been found in a variety of habitats, such as soil, seawater, sediment, rice paddies, honey, fish, and dried food.
Bacillus megaterium has been found to have a number of different uses. Specifically, it produces a variety of industrial enzymes such as penicillin acylase, various amylases, and glucose dehydrogenase (reviewed in, Vary, 2007). Additionally, a fermentation of B. megaterium ATCC 19213 grown to stationary phase was found to produce N-Deoxyschizokinen, a siderophore, which was identified as 4-[(3(acetylhydroxyamino) propyl) amino]-2-[2-[(3-(acetylamino) propyl) amino]-2-oxoethyl]-2-hydroxy-4-oxo-butanoic acid (Hu X and Boyer G. L, 1995). Schizokinen, a citrate-containing dihydroxamate, a siderophore has been produced by B. megaterium and Anabaena sp (Plowman J. E. et al 1984). The involvement of the citrate □-hydroxycarboxylate moiety in iron chelation was investigated by comparing the iron binding behavior of schizokinen with that of acetylschizokinen, a derivative in which the citrate hydroxyl group was modified by acetylation.
Another set of uses for products derived from Bacillus megaterium has been medicinal uses. BMG 59-R2, a peptide antibiotic, has been reported from B. megaterium (FERM-p 6177). The compound also inhibits alkaline phosphatase and tumour growth (Japan. Pat., 83 164 561. (1983)). Fermentation culture of B. megaterium in the presence of ansatrienin produces T23V and T23VI (Damberg, M. et al 1982). These compounds belong to the class of macrolides antibiotics, which also exhibit antitumor activity. A nucleoside named oxetanocin was isolated from B. megaterium NK84-0218 and the structure was determined to be 9-[(2R,3R,4S)-3,4-bis(hydroxymethyl)-2-oxetanyl]adenine by X-ray crystallographic analysis (Shimada N. et a., 1986). Oxetanocin showed activity against herpes simplex virus-II (DNA virus) at 5.8 pg/well (50% inhibition of cytopathic effect), while the cytotoxicity against Vero cells was 132.6 □g/well (50% inhibition of cell growth). Later, the derivatives of oxetanocin such as oxetanocins H, X, G and 2-aminooxetanocin A (Shimada N. et a., 1987) are isolated from the same strain which showed antiviral activities against herpes simplex virus type-II (HSV-II) and antiviral activities against human immunodeficiency virus. B. megaterium IFO 12108 (Nakahama, K. et al., 1981) was used for the microbial transformation of anamtiocin, an antitumor antibiotic produced by Nocardia sp. C-15003 (N-1). Ansamitocin P-3 was converted into 15-hydroxyansamitocin P-3 (PHO-3), and 15-epi-15-hydroxyansamitocin P-3 (epi-PHO-3), by using B. megaterium (Izawa M. et al., 1981). The microbial conversion product of P-3, has greater antitumor activities against P 388 and L 1210 than the substrate P-3.
Various isolates of Bacillus megaterium have been used as insecticides, bactericides, fungicides and nematicides (see, for example, Aksoy, H. M. 2008; U.S. Pat. Nos. 6,599,503, 7,906,131, 7,935,360). Some of these B. megaterium isolates have been used in combination with other bacteria to treat sludge and wastes such as Artemisia annua residue, flue dust, bran powder, feces of livestock and poultry, peat, and crop straw (see, for example, U.S. Pat. No. 7,279,104).